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Abstract:

A method for an SS to perform network entry in a multi-carrier wireless
environment that has a primary carrier and at least one secondary carrier
associated with a BS, the method comprising: a. sensing a carrier in an
area serviced by the BS; b. determining if the carrier is a primary
carrier or a secondary carrier; and c, performing the network entry if
the determining establishes that the sensed carrier is a primary carrier
and not a secondary carrier.

Claims:

1. A method for an SS to perform network entry in a multi-carrier
wireless environment that has a primary carrier and at least one
secondary carrier associated with a BS, the method comprising: a. sensing
a carrier in a primary carrier or a secondary carrier; b. determining if
the carrier is a primary carrier or a secondary carrier; c. performing
the network entry if the determining establishes that the sensed carrier
is a primary carrier and not a secondary carrier.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is the first application for the present disclosure.

MICROFICHE APPENDIX

[0002] Not applicable.

TECHNICAL FIELD

[0003] This application relates to wireless communication techniques in
general, and to technique of the disclosure, in particular.

ART RELATED TO THE APPLICATION

[0004] Draft IEEE 802.16m System Description Document, IEEE
802.16m-08/003r1, dated Apr. 15, 2008, it is stated that: [0005] This
[802.16m] standard amends the IEEE 802.16 WirelessMAN-OFDMA specification
to provide an advanced air interface for operation in licensed bands. It
meets the cellular layer requirements of IMT-Advanced next generation
mobile networks. This amendment provides continuing support for legacy
WirelessMAN-01-DMA equipment. [0006] And the standard will address the
following purpose: [0007] i. The purpose of this standard is to provide
performance improvements necessary to support future advanced services
and applications, such as those described by the ITU in Report ITU-R
M.2072.

[0009] Aspects and features of the present application will become
apparent to those ordinarily skilled in the art upon review of the
following description of specific embodiments of a disclosure in
conjunction with the accompanying drawing figures and appendices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Embodiments of the present application will now be described, by
way of example only, with reference to the accompanying drawing figures,
wherein:

[0024] Like reference numerals are used in different figures to denote
similar elements.

DETAILED DESCRIPTION OF THE DRAWINGS

Wireless System Overview

[0025] Referring to the drawings, FIG. 1 shows a base station controller
(BSC) 10 which controls wireless communications within multiple cells 12,
which cells are served by corresponding base stations (BS) 14. In some
configurations, each cell is further divided into multiple sectors 13 or
zones (not shown). In general, each base station 14 facilitates
communications using OFDM with mobile and/or wireless terminals 16, which
are within the cell 12 associated with the corresponding base station 14.
The movement of the mobile terminals 16 in relation to the base stations
14 results in significant fluctuation in channel conditions. As
illustrated, the base stations 14 and mobile terminals 16 may include
multiple antennas to provide spatial diversity for communications. In
some configurations, relay stations 15 may assist in communications
between base stations 14 and wireless terminals 16. Wireless terminals 16
can be handed off 18 from any cell 12, sector 13, zone (not shown), base
station 14 or relay 15 to an other cell 12, sector 13, zone (not shown),
base station 14 or relay 15. In some configurations, base stations 14
communicate with each and with another network (such as a core network or
the internet, both not shown) over a backhaul network 11. In some
configurations, a base station controller 10 is not needed.

[0026] With reference to FIG. 2, an example of a base station 14 is
illustrated. The base station 14 generally includes a control system 20,
a baseband processor 22, transmit circuitry 24, receive circuitry 26,
multiple antennas 28, and a network interface 30. The receive circuitry
26 receives radio frequency signals bearing information from one or more
remote transmitters provided by mobile terminals 16 (illustrated in FIG.
3) and relay stations 15 (illustrated in FIG. 4). A low noise amplifier
and a filter (not shown) may cooperate to amplify and remove broadband
interference from the signal for processing. Downconversion and
digitization circuitry (not shown) will then downconvert the filtered,
received signal to an intermediate or baseband frequency signal, which is
then digitized into one or more digital streams.

[0027] The baseband processor 22 processes the digitized received signal
to extract the information or data bits conveyed in the received signal.
This processing typically comprises demodulation, decoding, and error
correction operations. As such, the baseband processor 22 is generally
implemented in one or more digital signal processors (DSPs) or
application-specific integrated circuits (ASICs). The received
information is then sent across a wireless network via the network
interface 30 or transmitted to another mobile terminal 16 serviced by the
base station 14, either directly or with the assistance of a relay 15.

[0028] On the transmit side, the baseband processor 22 receives digitized
data, which may represent voice, data, or control information, from the
network interface 30 under the control of control system 20, and encodes
the data for transmission. The encoded data is output to the transmit
circuitry 24, where it is modulated by one or more carrier signals having
a desired transmit frequency or frequencies. A power amplifier (not
shown) will amplify the modulated carrier signals to a level appropriate
for transmission, and deliver the modulated carrier signals to the
antennas 28 through a matching network (not shown). Modulation and
processing details are described in greater detail below.

[0029] With reference to FIG. 3, an example of a mobile terminal 16 is
illustrated. Similarly to the base station 14, the mobile terminal 16
will include a control system 32, a baseband processor 34, transmit
circuitry 36, receive circuitry 38, multiple antennas 40, and user
interface circuitry 42. The receive circuitry 38 receives radio frequency
signals bearing information from one or more base stations 14 and relays
15. A low noise amplifier and a filter (not shown) may cooperate to
amplify and remove broadband interference from the signal for processing.
Downconversion and digitization circuitry (not shown) will then
downconvert the filtered, received signal to an intermediate or baseband
frequency signal, which is then digitized into one or more digital
streams.

[0030] The baseband processor 34 processes the digitized received signal
to extract the information or data bits conveyed in the received signal.
This processing typically comprises demodulation, decoding, and error
correction operations. The baseband processor 34 is generally implemented
in one or more digital signal processors (DSPs) and application specific
integrated circuits (ASICs).

[0031] For transmission, the baseband processor 34 receives digitized
data, which may represent voice, video, data, or control information,
from the control system 32, which it encodes for transmission. The
encoded data is output to the transmit circuitry 36, where it is used by
a modulator to modulate one or more carrier signals that is at a desired
transmit frequency or frequencies. A power amplifier (not shown) will
amplify the modulated carrier signals to a level appropriate for
transmission, and deliver the modulated carrier signal to the antennas 40
through a matching network (not shown). Various modulation and processing
techniques available to those skilled in the art are used for signal
transmission between the mobile terminal and the base station, either
directly or via the relay station.

[0032] In OFDM modulation, the transmission band is divided into multiple,
orthogonal carrier waves. Each carrier wave is modulated according to the
digital data to be transmitted. Because OFDM divides the transmission
band into multiple carriers, the bandwidth per carrier decreases and the
modulation time per carrier increases. Since the multiple carriers are
transmitted in parallel, the transmission rate for the digital data, or
symbols, on any given carrier is lower than when a single carrier is
used.

[0033] OFDM modulation utilizes the performance of an Inverse Fast Fourier
Transform (IFFT) on the information to be transmitted. For demodulation,
the performance of a Fast Fourier Transform (FFT) on the received signal
recovers the transmitted information. In practice, the IFFT and FFT are
provided by digital signal processing carrying out an Inverse Discrete
Fourier Transform (IDFT) and Discrete Fourier Transform (DFT),
respectively. Accordingly, the characterizing feature of OFDM modulation
is that orthogonal carrier waves are generated for multiple bands within
a transmission channel. The modulated signals are digital signals having
a relatively low transmission rate and capable of staying within their
respective bands. The individual carrier waves are not modulated directly
by the digital signals. Instead, all carrier waves are modulated at once
by IFFT processing.

[0034] In operation, OFDM is preferably used for at least downlink
transmission from the base stations 14 to the mobile terminals 16. Each
base station 14 is equipped with "n" transmit antennas 28 (n>=1), and
each mobile terminal 16 is equipped with "m" receive antennas 40
(m>=1). Notably, the respective antennas can be used for reception and
transmission using appropriate duplexers or switches and are so labelled
only for clarity.

[0035] When relay stations 15 are used, OFDM is preferably used for
downlink transmission from the base stations 14 to the relays 15 and from
relay stations 15 to the mobile terminals 16.

[0036] With reference to FIG. 4, an example of a relay station 15 is
illustrated. Similarly to the base station 14, and the mobile terminal
16, the relay station 15 will include a control system 132, a baseband
processor 134, transmit circuitry 136, receive circuitry 138, multiple
antennas 130, and relay circuitry 142. The relay circuitry 142 enables
the relay 14 to assist in communications between a base station 16 and
mobile terminals 16. The receive circuitry 138 receives radio frequency
signals bearing information from one or more base stations 14 and mobile
terminals 16. A low noise amplifier and a filter (not shown) may
cooperate to amplify and remove broadband interference from the signal
for processing. Downconversion and digitization circuitry (not shown)
will then downconvert the filtered, received signal to an intermediate or
baseband frequency signal, which is then digitized into one or more
digital streams.

[0037] The baseband processor 134 processes the digitized received signal
to extract the information or data bits conveyed in the received signal.
This processing typically comprises demodulation, decoding, and error
correction operations. The baseband processor 134 is generally
implemented in one or more digital signal processors (DSPs) and
application specific integrated circuits (ASICs).

[0038] For transmission, the baseband processor 134 receives digitized
data, which may represent voice, video, data, or control information,
from the control system 132, which it encodes for transmission. The
encoded data is output to the transmit circuitry 136, where it is used by
a modulator to modulate one or more carrier signals that is at a desired
transmit frequency or frequencies. A power amplifier (not shown) will
amplify the modulated carrier signals to a level appropriate for
transmission, and deliver the modulated carrier signal to the antennas
130 through a matching network (not shown). Various modulation and
processing techniques available to those skilled in the art are used for
signal transmission between the mobile terminal and the base station,
either directly or indirectly via a relay station, as described above.

[0039] With reference to FIG. 5, a logical OFDM transmission architecture
will be described. Initially, the base station controller 10 will send
data to be transmitted to various mobile terminals 16 to the base station
14, either directly or with the assistance of a relay station 15. The
base station 14 may use the channel quality indicators (CQIs) associated
with the mobile terminals to schedule the data for transmission as well
as select appropriate coding and modulation for transmitting the
scheduled data. The CQIs may be directly from the mobile terminals 16 or
determined at the base station 14 based on information provided by the
mobile terminals 16. In either case, the CQI for each mobile terminal 16
is a function of the degree to which the channel amplitude (or response)
varies across the OFDM frequency band.

[0040] Scheduled data 44, which is a stream of bits, is scrambled in a
manner reducing the peak-to-average power ratio associated with the data
using data scrambling logic 46. A cyclic redundancy check (CRC) for the
scrambled data is determined and appended to the scrambled data using CRC
adding logic 48. Next, channel coding is performed using channel encoder
logic 50 to effectively add redundancy to the data to facilitate recovery
and error correction at the mobile terminal 16. Again, the channel coding
for a particular mobile terminal 16 is based on the CQI. In some
implementations, the channel encoder logic 50 uses known Turbo encoding
techniques. The encoded data is then processed by rate matching logic 52
to compensate for the data expansion associated with encoding.

[0041] Bit interleaver logic 54 systematically reorders the bits in the
encoded data to minimize the loss of consecutive data bits. The resultant
data bits are systematically mapped into corresponding symbols depending
on the chosen baseband modulation by mapping logic 56. Preferably,
Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key
(QPSK) modulation is used. The degree of modulation is preferably chosen
based on the CQI for the particular mobile terminal. The symbols may be
systematically reordered to further bolster the immunity of the
transmitted signal to periodic data loss caused by frequency selective
fading using symbol interleaver logic 58.

[0042] At this point, groups of bits have been mapped into symbols
representing locations in an amplitude and phase constellation. When
spatial diversity is desired, blocks of symbols are then processed by
space-time block code (STC) encoder logic 60, which modifies the symbols
in a fashion making the transmitted signals more resistant to
interference and more readily decoded at a mobile terminal 16. The STC
encoder logic 60 will process the incoming symbols and provide "n"
outputs corresponding to the number of transmit antennas 28 for the base
station 14. The control system 20 and/or baseband processor 22 as
described above with respect to FIG. 5 will provide a mapping control
signal to control STC encoding. At this point, assume the symbols for the
"n" outputs are representative of the data to be transmitted and capable
of being recovered by the mobile terminal 16.

[0043] For the present example, assume the base station 14 has two
antennas 28 (n=2) and the STC encoder logic 60 provides two output
streams of symbols. Accordingly, each of the symbol streams output by the
STC encoder logic 60 is sent to a corresponding IFFT processor 62,
illustrated separately for ease of understanding. Those skilled in the
art will recognize that one or more processors may be used to provide
such digital signal processing, alone or in combination with other
processing described herein. The IFFT processors 62 will preferably
operate on the respective symbols to provide an inverse Fourier
Transform. The output of the IFFT processors 62 provides symbols in the
time domain. The time domain symbols are grouped into frames, which are
associated with a prefix by prefix insertion logic 64. Each of the
resultant signals is up-converted in the digital domain to an
intermediate frequency and converted to an analog signal via the
corresponding digital up-conversion (DUC) and digital-to-analog (D/A)
conversion circuitry 66. The resultant (analog) signals are then
simultaneously modulated at the desired RF frequency, amplified, and
transmitted via the RF circuitry 68 and antennas 28. Notably, pilot
signals known by the intended mobile terminal 16 are scattered among the
sub-carriers. The mobile terminal 16, which is discussed in detail below,
will use the pilot signals for channel estimation.

[0044] Reference is now made to FIG. 6 to illustrate reception of the
transmitted signals by a mobile terminal 16, either directly from base
station 14 or with the assistance of relay 15. Upon arrival of the
transmitted signals at each of the antennas 40 of the mobile terminal 16,
the respective signals are demodulated and amplified by corresponding RF
circuitry 70. For the sake of conciseness and clarity, only one of the
two receive paths is described and illustrated in detail.
Analog-to-digital (A/D) converter and down-conversion circuitry 72
digitizes and downconverts the analog signal for digital processing. The
resultant digitized signal may be used by automatic gain control
circuitry (AGC) 74 to control the gain of the amplifiers in the RF
circuitry 70 based on the received signal level.

[0045] Initially, the digitized signal is provided to synchronization
logic 76, which includes coarse synchronization logic 78, which buffers
several OFDM symbols and calculates an auto-correlation between the two
successive OFDM symbols. A resultant time index corresponding to the
maximum of the correlation result determines a fine synchronization
search window, which is used by fine synchronization logic 80 to
determine a precise framing starting position based on the headers. The
output of the fine synchronization logic 80 facilitates frame acquisition
by frame alignment logic 84. Proper framing alignment is important so
that subsequent FFT processing provides an accurate conversion from the
time domain to the frequency domain. The fine synchronization algorithm
is based on the correlation between the received pilot signals carried by
the headers and a local copy of the known pilot data. Once frame
alignment acquisition occurs, the prefix of the OFDM symbol is removed
with prefix removal logic 86 and resultant samples are sent to frequency
offset correction logic 88, which compensates for the system frequency
offset caused by the unmatched local oscillators in the transmitter and
the receiver. Preferably, the synchronization logic 76 includes frequency
offset and clock estimation logic 82, which is based on the headers to
help estimate such effects on the transmitted signal and provide those
estimations to the correction logic 88 to properly process OFDM symbols.

[0046] At this point, the OFDM symbols in the time domain are ready for
conversion to the frequency domain using FFT processing logic 90. The
results are frequency domain symbols, which are sent to processing logic
92. The processing logic 92 extracts the scattered pilot signal using
scattered pilot extraction logic 94, determines a channel estimate based
on the extracted pilot signal using channel estimation logic 96, and
provides channel responses for all sub-carriers using channel
reconstruction logic 98. In order to determine a channel response for
each of the sub-carriers, the pilot signal is essentially multiple pilot
symbols that are scattered among the data symbols throughout the OFDM
sub-carriers in a known pattern in both time and frequency. Continuing
with FIG. 6, the processing logic compares the received pilot symbols
with the pilot symbols that are expected in certain sub-carriers at
certain times to determine a channel response for the sub-carriers in
which pilot symbols were transmitted. The results are interpolated to
estimate a channel response for most, if not all, of the remaining
sub-carriers for which pilot symbols were not provided. The actual and
interpolated channel responses are used to estimate an overall channel
response, which includes the channel responses for most, if not all, of
the sub-carriers in the OFDM channel.

[0047] The frequency domain symbols and channel reconstruction
information, which are derived from the channel responses for each
receive path are provided to an STC decoder 100, which provides STC
decoding on both received paths to recover the transmitted symbols. The
channel reconstruction information provides equalization information to
the STC decoder 100 sufficient to remove the effects of the transmission
channel when processing the respective frequency domain symbols.

[0048] The recovered symbols are placed back in order using symbol
de-interleaver logic 102, which corresponds to the symbol interleaver
logic 58 of the transmitter. The de-interleaved symbols are then
demodulated or de-mapped to a corresponding bitstream using de-mapping
logic 104. The bits are then de-interleaved using bit de-interleaver
logic 106, which corresponds to the bit interleaver logic 54 of the
transmitter architecture. The de-interleaved bits are then processed by
rate de-matching logic 108 and presented to channel decoder logic 110 to
recover the initially scrambled data and the CRC checksum. Accordingly,
CRC logic 112 removes the CRC checksum, checks the scrambled data in
traditional fashion, and provides it to the de-scrambling logic 114 for
de-scrambling using the known base station de-scrambling code to recover
the originally transmitted data 116.

[0049] In parallel to recovering the data 116, a CQI, or at least
information sufficient to create a CQI at the base station 14, is
determined and transmitted to the base station 14. As noted above, the
CQI may be a function of the carrier-to-interference ratio (CR), as well
as the degree to which the channel response varies across the various
sub-carriers in the OFDM frequency band. For this embodiment, the channel
gain for each sub-carrier in the OFDM frequency band being used to
transmit information is compared relative to one another to determine the
degree to which the channel gain varies across the OFDM frequency band.
Although numerous techniques are available to measure the degree of
variation, one technique is to calculate the standard deviation of the
channel gain for each sub-carrier throughout the OFDM frequency band
being used to transmit data.

[0050] In some embodiments, a relay station may operate in a time division
manner using only one radio, or alternatively include multiple radios.

[0051] FIGS. 1 to 6 provide one specific example of a communication system
that could be used to implement embodiments of the application. It is to
be understood that embodiments of the application can be implemented with
communications systems having architectures that are different than the
specific example, but that operate in a manner consistent with the
implementation of the embodiments as described herein.

[0053] The description of these figures in of IEEE 802.16m-08/003r1 is
incorporated herein by reference.

Further Details of Present Disclosure

[0054] Details of embodiments of the present disclosure are in the
attached appendices.

[0055] The above-described embodiments of the present application are
intended to be examples only. Those of skill in the art may effect
alterations, modifications and variations to the particular embodiments
without departing from the scope of the application.